Final answer:
In a cross of pure-breeding purple and white plants, if flower color is controlled by two genes interacting additively, the phenotypic ratio in the F2 generation, which may reflect this type of inheritance, would likely be 15:1.
Step-by-step explanation:
The question is related to Mendelian genetics and the inheritance pattern of flower colors in a hypothetical plant species. When a pure-breeding purple plant is crossed with a pure-breeding white plant, the F1 generation results in all purple flowers. If flower color is controlled by two genes that interact additively, the expected phenotypic ratio for the F2 generation with four possible flower colors (purple, blue, red, or white), could be 9:3:3:1. However, this classic 9:3:3:1 ratio is characteristic of a dihybrid cross involving independent assortment without gene interaction. The question prompts us to consider gene interaction resulting in additive effects, which can alter the expected Mendelian ratios.
For additive gene interactions, where the presence of each dominant allele contributes to the final phenotype incrementally, the phenotypic ratio that may reflect this type of inheritance is 9:3:4 (with 9 parts expressing the dominant phenotype, 3 parts expressing one dominant trait and one recessive trait combination, and 4 parts expressing the recessive phenotype). Considering the final answer in relation to the given data would be a 15:1 ratio, this suggests strong additive effects where only the double recessive genotype leads to the white phenotype, making the 15:1 ratio more indicative of two gene pairs contributing additively to the phenotype.
In the F2 generation, as mentioned, if three out of every four plants have purple flowers (75%), this ratio does not match a simple Mendelian 3:1 ratio; so, for two genes interacting additively, the flower color segregation ratio that may be observed is more likely to be 15:1.